A known method of producing D-tryptophan comprises contacting D,L-indolyl methylhydantoin with microorganisms capable of selectively hydrolyzing D-indolyl methylhydantoin into N-carbamoyl-D-tryptophan to synthesize N-carbamoyl-D-tryptophan and hydrolyzing the resulting N-carbamoyl-D-tryptophan into D-tryptophan chemically with nitrous acid or the like or by using microorganisms (Hydantoinase method, JP-A-Sho 61-17791).
It is also known to produce D-tryptophan by contacting D,L-tryptophanamide with microorganisms or an enzyme, which are capable of producing D-tryptophan to selectively hydrolyze D-tryptophanamide, (D-Amidase method, JP-B-Hei 8-22228), and by selectively degrading D,L-tryptophanamide L-tryptophanamide and chemically hydrolyzing the remaining D-tryptophanamide (L-Amidase method, JP-A-Sho 57-13000).
In addition, other methods for producing D-tryptophan includes the method in which D-tryptophan is produced from indole pyruvate and D-alanine as an amino group donor by the action of D-amino acid transaminase (Transaminase method, JP-B-Hei 7-85718), the method which comprises contacting N-acetyl-D,L-tryptophan with L-aminoacylase to selectively deacetylate N-acetyl-L-tryptophan and chemically deacetylating the remaining N-acetyl-D-tryptophan (L-aminoacylase method, Methods in Enzymology 3, 554-570, (1957)), the method which comprises contacting N-acetyl-D,L-tryptophan with D-aminoacylase to selectively deacylate N-acetyl-D-tryptophan (D-aminoacylase method, JP-B-Hei 01-29560), and the method which comprises converting D-tryptophan in D,L-tryptophan selectively into N-acetyl-D-tryptophan with D-amino acid acetyltransferase to separate D-tryptophan from L-tryptophan and chemically hydrolyzing the resulting N-acetyl-D-tryptophan (Acetyltransferase method, JP-A-Sho 60-251892).
In view of industrial production of D-tryptophan, these methods have such disadvantages as expensiveness of the substrates, the complicated reaction procedures, the low yield, and the low optical purity.